Definition - What does Inoculum mean?

Inoculum (plural: inocula) is the active material used in an inoculation. In metallurgy or engineering, an is alloyant used to refine grains in a cast macrostructure as inocula. It is used to treat molten metal chemically to strengthen the microstructure.

The inoculum may be derived from a variety of sources:

  • Activated sludge
  • Sewage effluent (nonchlorinated)
  • Surface waters and soils
  • Mixture of these materials

Corrosionpedia explains Inoculum

Inoculum is used to implement grain boundary strengthening in metallurgy, as it is a grain refiner. The specific techniques and corresponding mechanisms vary based on what materials are being processed.

One method for controlling grain size in aluminum alloys is by introducing particles to serve as nucleants, such as Al-5%Ti. Grains grow via heterogeneous nucleation. Solute particles can then be added (called grain refiners) which limit the growth of dendrites, leading to grain refinement. Titanium diboride (TiB2) is a common grain refiner for aluminum alloys; however, novel grain refiners such as aluminum-scandinium (Al3Sc) have been suggested.

Current grain-refinement practice involves the addition of master alloys before casting, introducing inoculant particles to the melt. These particles act as nucleation points for a-Al grains, resulting in a uniformly fine, equiaxed as cast microstructure. The grain refiners aluminum-titanium-boron (Al-Ti-B) and aluminum-titanium-carbon (Al-Ti-C) are used here. Grain refinement of aluminum and its alloys improves the mechanical properties of casting as well as other properties, such as surface finish.

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